Research On Proton Exchange Membrane’s Hydrophilicity

Proton Exchange Membrane Fuel Cell(PEMFC)is one of the most novel and promising energy-converting devices which can convert chemical energy to electrical energy directly and has been widespread used in various field such as new energy vehicles,standby power,distributed power station and so on because of its advantages like of high energy conversion efficiency,environmentally friendly,ability to start-up at low temperature.As a key component of PEMFC,PEM plays an important role in the water management of PEMFC.However,there are few reports on the properties of membrane surface combined with water,especially the effect of the membranes with low EW value and the heat treatment temperature during the preparation of the membrane electrode assemble,which can provide reference for different types of membranes used in different humidity applications and temperature control during the preparation of membrane electrodes.Therefore,it is very important to study the surface property of the PEM under different conditions in PEMFC.In this paper,the surface hydrophilicity of PEM under different humidity and difference annealed temperature have been studied.Firstly,lithium chloride solution(LiCl)has been chose to control humidity in our paper through comparing several methods about controlling humidity.The vapor pressure on the surface of lithium chloride solution was computed.And humidity could be controlled under a range of 19.6% to 86.7%.The vapor pressure on the surface of lithium chloride solution had been experimentally verified,the deviation is less than 5% which indicating the feasibility of our experiment.Secondly,the hydrophilicity of PEM with different EW values under different humidity have been studied using designed method.With increasing the relative humidity,the surface contact angle of PEM with different EW value decreased and all become more hydrophilic.Furthermore,the hydrophilicity increases with the decrease of EW value.especially the E membrane with the lowest EW value of 820 had the smallest contact angle value which decreased from 79.3° to 68.6°.Thirdly,surface property of Nafion211 membrane annealed under difference temperature have been studied through contact angle,AFM and XPS.The results showed that increased the annealing temperature.The surface features height(i.e.surface roughness)of the membrane gradually increased with increasing annealed temperature and had a largest change at 175℃ which increased to 59 nm.The content of F element on the surface of PEM increased with increasing annealed temperature which indicated that annealed temperature would enlarge the hydrophobicity of PEM.